I want to implement smooth cornering in a grid, much like Pacman moving in his maze. A big difference with Pacman, my characters can stop- thus the player has to keep pressing the controls to keep moving.
I also want the speed of the character to be variable (depending on various game mechanics). Now this felt like a simple mechanic to code, however it's giving me more trouble than I expected. The code only works properly if the character aligns exactly with the tiles.
The green character moves down and the player want to enter the corridor on the right. However the character doesn't align properly thus the collision prevents it from moving.
Now the character "jumps" noticably if I did my collision check on the center of the character. I wanted the character corner a bit earlier to give the player some wiggle room. Thus I implemented 8 collision points:
It also keeps the character nicely aligned to the grid. All seemed fine until this happened:
The character keeps bouncing back and forth as the collision code pushed the character out of the colliding boundaries.
I feel my code is getting more complex than needed. I googled to check various pacman implementations, but most I found deal with fixed speeds and rely on the fact that pacman keeps moving.
So what is the best way to deal with navigating a gridlike maze with variable speeds?
My game is in Monogame (C#) my maze is an array of tiles[x][y].
My current collision code goes like this:
For each collision point I check the tile in it's path (to prevent bullet through paper- while my character won't go as fast- I might get projectiles in the game later).
TileData tileinpath = Line(X0, Y0, X1, Y1, new Vector2(obj.PosX + obj.CollisionPoints[i].RelativePosition.X, obj.PosY + obj.CollisionPoints[i].RelativePosition.Y)); Line is Bresenham on my tilemap to return the nearest tile in the collision path. Then depending on the location of the collisionpoint:
case CollisionPosition.BottomRight: if (moveY <= 0) //check if we're really moving that direction break; //apparently we hit something, so adjust everything accordingly. obj.SpeedY = 0; //stop movement in that direction. obj.PosY = tileinpath.Y * CollisionMap.TileHeight - obj.BoundingBox.Height / 2; obj.CollisionPoints[i].CollisionDetected = true; break; Can the grid movement be done simpeler? What am I missing ...
EDIT, based on solution:
I ended up using VaTTeRGeR suggestion. I have the character move from tile center to tilecenter and make decisions based on the options whenever the character crosses a tilecenter.
public void NavigateTo(Entities.Mobile mobile, Entities.Mobile.Direction intendeddirection, float dt) { Entities.Mobile.Direction CurrentDirection = mobile.CurrentDirection; //current direction of travel. float DeltaMove = mobile.Speed * dt; //amount of pixels moved in this frame. //what is our current tile? int currentTileX = MathHelper.Clamp((int)mobile.Position.X / CollisionMap.TileWidth, 0, CollisionMap.Width - 1); int currentTileY = MathHelper.Clamp((int)mobile.Position.Y / CollisionMap.TileHeight, 0, CollisionMap.Height - 1); Vector2 TileCenter = new Vector2(currentTileX * CollisionMap.TileWidth + CollisionMap.TileWidth / 2, currentTileY * CollisionMap.TileHeight + CollisionMap.TileHeight / 2); //determine the position compared to the centernode. bool IsInFrontOfNode = InFrontOfNode(mobile.Position, TileCenter, CurrentDirection); bool IsTargetPastOfNode = PastOfNode(mobile.Position, TileCenter, DeltaMove, CurrentDirection); bool WantsToReverse = Reversing(CurrentDirection, intendeddirection); if (IsInFrontOfNode) { if (WantsToReverse) { //it is assumed that the check to get here was already done. //the wants to reverse check already made sure we are moving in the revers direction of the travel direction MoveInDirection(mobile, intendeddirection, DeltaMove); return; } if (!IsTargetPastOfNode) //we're still in front of our node. { //Safely move the direction we were moving. MoveInDirection(mobile, CurrentDirection, DeltaMove); return; } //so now we're here: //the mobile wants to move past a node and can potentially change direction here. //check if we can move in the direction we want. if (intendeddirection != CurrentDirection) { //we want to change directions! if (IsTileAvailableInDirection(currentTileX, currentTileY, intendeddirection)) { //yes we can move that way. //how much can we move in the new direction? float remaining = RemainingMove(mobile.Position, TileCenter, DeltaMove, CurrentDirection); //first move to the node. mobile.Position = TileCenter; //now move the remainder of the move. MoveInDirection(mobile, intendeddirection, remaining); return; } //no way, there is no tile over there. } //try to move in the current direction. if(IsTileAvailableInDirection(currentTileX,currentTileY,CurrentDirection)) { //we can still move that direction. MoveInDirection(mobile, CurrentDirection,DeltaMove); return; } //we can not move further than the node (tilecenter). mobile.Position=TileCenter; return; } if (!IsInFrontOfNode) { //past the node. we can only reverse or continue in the direction we're moving in. if (WantsToReverse) { //it is assumed that the check to get here was already done. //the wants to reverse check already made sure we are moving in the revers direction of the travel direction MoveInDirection(mobile, intendeddirection, DeltaMove); return; } //we should already have checked this some frames ago, but there is no harm in checking each frame... //try to move in the current direction. if(IsTileAvailableInDirection(currentTileX,currentTileY,CurrentDirection)) { //we can still move that direction. MoveInDirection(mobile, CurrentDirection,DeltaMove); return; } //we can not move further than the node (tilecenter). mobile.Position=TileCenter; return; } } The helper functions do some minor calculations where the axis (X,Y) and relation to direction are relevant.
